Have Democratic presidents ever tweeted/emailed/promoted/sent out doctored videos that make their rivals look bad?

The video Orange man posted on twitter wasn't doctored. Media has changed the definition of doctored to suit them. It was edited to show only relevant parts but there was nothing fake about it.

Why not let media show the original so called undoctored version?

The reporting I saw on this was:

https://www.nytimes.com/2019/05/24/us/politics/pelosi-doctor...

Video at top has her speaking at normal pace, and then shows a slowed-down version. Is this something you dispute? I have not followed the story at all, beyond seeing that article.

Can you give an example that's on the scale of Pelosi?

Trying to take myself away from my own biases, perhaps you can say Trump but coming from the executive branch you could say he's not that comparable, also people on both sides have called him outrageous.

More direct comparisons would be Paul Ryan, Boehner, Newt Gingrich. I didn't see them getting Pelosi-scale smearing.

You mean something like "If you like your health care plan you can keep it"? ...or how about the "anti-muslim video that spurned spontaneous protests" across the middle east? In any event, by and large, most doctoring / half-truths are initiated by major news sources, and the majority of these defame Republicans and/or Republican ideals. It would be redundant for democratic politicians to get involved.